1988 240 Hard Starting When Cold

Roger M · Post by **Roger M** » 01 Oct 2014, 09:53

Hello all

I'm new here, and have a 1988 240 DL Wagon with a 5 speed manual transmission. I've owned it for a couple years and fixed a bunch of its issues along the way.

This week, it has been hard to start when cold. In order to get it started, I have to hold the throttle halfway to the floor while turning over the engine for about 20 seconds. It coughs and sputters and finally runs. It will run on it's own then, but hesitates when it press the gas pedal until it is completely warmed up. At that point the car runs fine.

*I did have someone turn the key on, and I listened for the in tank pump. It seems to be working fine.

* I unplugged the Mass airflow sensor plug while the engine was running and warm. The idle dropped slightly and seemed to run a bit rougher.

*I did replace the coolant temperature sensor last winter when a similar thing happened. I had to hold the throttle down as I'm doing now in order to get it running. However, it would not idle on it's own until warmed up. Replacing the Coolant temp sensor cured this.

Any help or constructive input is greatly appreciated

93Regina · Post by **93Regina** » 01 Oct 2014, 19:47

Roger M wrote:This week, it has been hard to start when cold.

IAC Valve Cleaning = Cold Starting Improvement

First the smart part – I followed Lee’s advice and removed and cleaned the throttle body and IAC valve they were both filthy and needed a major cleaning – it made a huge difference on the cold morning start ups.

Make sure throttle switch is contacting when in idle position.

Roger M · Post by **Roger M** » 02 Oct 2014, 09:16

Thanks for the advice, 93Regina

Update: I replaced the fuel filter yesterday(as it was cheap and easy to fix). This morning the car started right up! So it seems as though I've found and fixed the problem.

However, cleaning the IAC valve and throttle body sounds like some good preventative maintenance. I will go through that in the next few days.

Post by **jimmy57** » 02 Oct 2014, 14:40

85-88 240 and 740 used LH 2.2. This system has a test lead for ECU output that indicates center range CO control. There is also a wire used for grounding a pin of the ECU that sets IAC to minimum duty cycle. These leads are on the left side fender in the area of the headlight relay on 240 and on the RH fender in front of strut housing on 740/760/780 with lh 2.2 engines ( B230F 85-88, B280 all years, or B230FT 85-89).

First thing it make sure there are no obvious air leaks, vacuum leaks, or other issues.
Then ground the idle test wire, the red/white one, and adjust idle speed to 725 RPM with the black knob on bottom of throttle assembly.

Now attach an LED test light (-) lead to the other test lead. The other lead from LED test light goes to 12V power. The output is ground pulse so an analog voltmeter will sweep with pulse and a digital meter will have higher voltage fluctuations and dancing bar graph if fitted.

The screw on MAF sensor has a screw down in a round boss that was covered (could still be covered) by an aluminum plug. If the plug is there drill a small hold 1/4 deep and screw in a screw and pull the plug out. The plug is only retained by a sprung still ring.
With engine at operating temp, idling, a/c off, out of gear attach the LED or other to the CO test lead. If the LED is not lit or voltmeter at nearly 0 V then the CO base point is low. IF the LED is lit or voltmeter shows upwards of battery voltage then CO base point is rich.
Adjust the screw CW to richen and CCW to lean. You are looking for a 50% rich/50% lean ideally at this step. This will be indicated by equal time lit vs. not lit or high voltage vs. low voltage.
Once you get a more or less 50/50 set point then turn the screw 3 turns CW.
The pulse at 50/50 means the short term fuel trim is increasing and decreasing equal amounts. The CO screw is a potentiometer that is an input to the ECU to alter base injector duration. This base value is the computational base point for fuel mixture and is the default mixture base point until O2 sensor is operating. If lean then the starting fuel enrichment is lean. The 3 turns CW is a learned setting that offsets the base for better cold start and driveability. Once warmed up the O2 sensor input will cause correction and emissions will be on point. The 3 turns offset is well within the ECU's capability to compensate for. Trust me, you'd rather your work a little bit to lean it out as opposed to working to richen it up.

I should mention that one of those things that must be in good working order is the engine coolant temp sensor. The one for fuel injection is by the third intake port on head. The easy one to get to at front of head is for coolant gauge on dash.

Roger M · Post by **Roger M** » 07 Oct 2014, 10:12

Thanks for that information, Jimmy57

So the car started fine in the morning for the first few days, until Sunday. On sunday it went back to hard starts in the morning. I took 93Regina's advice and cleaned the IAC valve, throttle body, as well as the MAF sensor. I didnt have any carb cleaner on hand, but did have a full can of electrical parts cleaner. I seems to work about the same as carb or FI cleaner. I did blow the tb and iac with compressed air following the spray cleaner.

Here's the TB before cleaning

so after a couple days of driving it, it seems to be starting good now. I'll monitor it for now and see if anything changes. Thanks all for the help.

Side note: The car feels a bit 'stronger' now that I've cleaned the FI components. It is a little faster up the hills and quicker out of the hole(maybe it's just my wishful thinking...).

Roger M · Post by **Roger M** » 08 Oct 2014, 10:44

Update: Problem is still there. The starter turns the engine over for 15 seconds without any sign of the car starting. On the second attempt, it starts after a few seconds and runs fine.

I'll go through the steps that Jimmy57 mentioned above here in the next couple of days. Any other helpful ideas are welcome. Thanks

lummert · Post by **lummert** » 08 Oct 2014, 13:19

Fuel pump check valve?

93Regina · Post by **93Regina** » 08 Oct 2014, 14:50

Roger M wrote:starter

Bump starter enough so fuel pumps are engaged...wait until fuel pumps stop...then start engine.

Roger M · Post by **Roger M** » 13 Oct 2014, 10:42

Update: The issue is still there

I found the in tank pump not working. I hooked up a jumper wire from fuse number 6 to number 4(in tank pump), and immediately heard the pump running. The car started up right away after that, but went to a VERY high idle until it warmed up.

There is no power at the number 4 fuse on either side. Does that point to the relay being faulty?

Thanks in advance for all the help.